Icom IC-705 LDG Z100 Plus Setup

Hello Operators
Many of us may have decided to use the Icom IC-705 with a broadband antenna system like a 9:1, 4:1 random wire, off centre fed dipole, or other type of non-resonant antenna system. If so, we would have gone through the process of banging our heads against the wall, trying to figure out a reliable option.

Because of its size, it might not necessarily be the most portable solution, but one of the “less portable” options is the LDG Z100Plus. It’s a budget option, easy to use, with an incredible layer of integration/automation already built-in, supporting the Icom IC-705. Perhaps it would be more accurate to say the Icom IC-705 supports the Z100Plus antenna tuner. Whichever way that development ball rolled, if you already have one, you’re in luck. If you’re wondering which desktop or mobile tuner to choose, this is a valid option.

Here’s an example of how the LDG Z100Plus is operated hands free, with the Icom IC-705. The radio is in complete control of the z100plus, leaving the operator free to do other tasks.

I can see how this functionality would be incredibly interesting for ALE, SELCAL, HamRing, WSPR, JS8Call, where one would like automatic tuning, when the frequency or band has changed.


For automated operation, a single control cable is required between the IC-705, and the Z100Plus.

This cable is nothing more than a female-female TRS, 3.5mm stereo extension cable, between the radio interface port on the tuner, and the tuner port on the IC-705. If you have previously used this tuner with the FT-891 for example, there is no Criss Cross of wires between connectors. It’s a straight through one-to-one connection eg tip-tip, ring-ring, sleeve-sleeve! This means you can fashion your own cable, or just grab a stereo extension cable from your local Hi-Fi shop, without breaking out the breadboard and multimeter to figure it out.

Once you connect that TRS cable between the tuner and the IC-705, the tuner icon which is normally grayed out on the 705, will become illuminated. At that point one short touch to take control of the tuner, then a long press to manually trigger a tuning cycle with the tuner. The tuning configuration will now be stored in the tuners memory. From that point on, if you change bands or frequencies, the tuner will provide a memory tune for frequencies or bands you’ve previously tuned. For new frequencies for bands, it will start an entirely new tuning cycle. Don’t worry if you happen to have changed the antenna, the radio will trigger a complete tuning cycle if the SWR threshold has been exceeded.

This is about it! Like I said earlier, this is quite a big tuner to use with such a small radio. I can imagine using this at home, mobile, but definitely not out in the field. The reason I’m sharing is the magnificent integration between this antenna tuner, and the Icom IC 705. The way they work together should be the Benchmark for operation and simplicity for all the other tuners, regardless of manufacturer. No special interface boxes, no controllers, just a TRS cable between the tuner and the radio.

Julian oh8stn

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